1. Field of the Invention
The present invention relates to extruder dies and, more particularly, to processes for repairing the worn inlet ports of extrusion channels in extruder dies.
2. Technical Background
Extruders are widely used in a number of industries, especially in the food industry. Edible material in powder or dough form is introduced into an extruder and then forced into an extruder die inlet port. The extruder die has the shape of the desired product. The extrudate will take the shape into which it is formed coming out through the extruder die outlet. The extrudate is generally continuous but can be cut into desired lengths after being extruded out of the die. In some extruder dies the inlet ports can become worn with use, resulting in increasing amounts of power or pressure required to force the material into the inlet ports and through extrusion channels. This can cause the motors driving the extruder to consume excessive energy and reduce the output of the extruder system.
FIG. 1 shows an example of a circular extruder die 10 having interior area 11. An extruder (not shown) is positioned within the interior area 11 and forces powdered or other type material into the inlet ports 16 positioned on the interior surface 12 of the extruder die 10. The inlet port 16 provides an opening into an extrusion channel 14 (see FIG. 2). The material is then forced through extrusion channels 14 to the exterior surface 13 of the extruder die 10, and out through exit port 17. As the material is forced out through exit port 17, the material can be cut into any desired lengths. In a proper and unworn condition of the extruder die 10, as shown in FIG. 2, the interior surface 12 forms an approximate right angle with the internal surface 15 of the extrusion channel 14. This creates a sharp edge on the inlet port 16. This sharp edge may be chamfered when extruding some materials to aid the product entrance into the extrusion channel. FIG. 3 illustrates worn inlet ports 18 where interior surface 12 and the worn inlet port 18 form a funnel shape. This effect of producing a worn inlet port 18 in an extruder die 10 can occur in a few days of operation when the extrudate is abrasive. There is no known practical or commercially feasible process for repairing the worn inlet ports 18 to restore them to their original sharp-edged condition. These types of extrusion dies 10 may contain thousands of inlet ports 16 and extrusion channels 14. Consequently it has been necessary to replace worn extruder die 10 with a new extruder die 10, which adds a significant expense to the product produced with the extruder die 10. What is needed is a simple, rapid, inexpensive process for restoring the worn inlet ports 18 of extrusion channels 14.